1. Field of the Invention
This invention relates to fluid expulsion devices and more specifically to a unique packaging system including a liquid containing bladder that resists flexure prior to expulsion of the liquid.
2. Description of the Prior Art
The instant invention has broad application in any system for transferring fluid in an uncontaminated state from a storage position to a different position. A liquid expulsion device constructed in accordance with the instant invention could be utilized in various environments such as in diver's equipment, underwater seacraft, aircraft maneuvering equipment and in many types of gas generators.
Some of the benefits and advantages of the instant invention can be realized, for example, whenever the container of a liquid to be expelled is sensitive to motion changes, temperature or pressure changes, or similar types of environmental changes. For the sake of clarity and simplicity, the environment which has been chosen to explain the instant invention pertains broadly to the gas generator art and more specifically, to the rocket-missile art.
One type of fluid expulsion system in present day use incorporates a fluid expulsion tank enclosing a bladder. When the bladder is subjected to a predetermined external pressure, it collapses and squeezes the fluid into a discharge line. In certain environments precautions must be taken to minimize the intensity and frequency of flexure in the bladder walls. Flexure can cause fatigue in the bladder and diminish its capacity to perform its intended function which is forcing the fluid out of the tank at a predetermined uniform discharge rate. Intensive flexure can rupture the bladder with consequential severe hazards.
It is important, therefore, to control and preferably eliminate bladder flexure. In rocket engine applications, for example, as the ambient temperature outside the tank decreases, there is a corresponding decrease in the propellant volume. Under ordinary circumstances there would be a greatly enlarged low pressure ullage in conventional tanks. The term ullage refers to the empty or gaseous space between the surface of a liquid in a container and the walls of the container. Conventional bladders are designed to have little or no ullage. Under decreasing temperature environments the bladder begins to separate from the wall and follow the surface of the contracting propellant volume. Increases in temperature would thereafter produce a corresponding increase in the propellant volume. This would force the bladder under flexure outwardly and eventually into engagement with the tank wall. Repetitious contractions and expansion of the propellant volume under such temperature cycling conditions would cause the flexure that the instant invention seeks to eliminate.
Even more dangerous to the life span of the bladder is a condition occurring when the propellant volume is in a contracted state and the tank experiences an abrupt motion change. This would promote sloshing by the propellant which is random liquid transfer or shifting from one location to another. Sloshing causes the liquid to press against the bladder, making it endure a great amount of strain and flexure which, as mentioned, might result in rupture.